In manufacturing semiconductor devices such as LSI and super-LSI or in manufacturing a liquid crystal display board or the like, a pattern is made by irradiating a light to a semiconductor wafer or an original plate for liquid crystal, but if a dust is attached a photo mask or a reticle (hereinafter collectively referred to as “photo mask” for simplicity) which is used during the irradiation operation, the dust causes the pattern to have roughened edges or black stains on a base, and thus leads to problems such as damaged dimensions, poor quality, and deformed external appearance.
Thus, these works are usually performed in a clean room, but it is still difficult to keep the photo mask clean all the time. Therefore, a pellicle is attached to a surface of the photo mask as a dust-fender before photo irradiation is carried out. Under such circumstances, foreign substances do not directly adhere to the surface of the photo mask but adhere only to the pellicle film, which is sufficiently away from the photo mask surface so that by setting a photo focus on a lithography pattern on the photo mask, the foreign substances on the pellicle film fail to transfer their shadows on the photo mask and thus no longer become a cause for problems to the image transfer performance.
In general, a pellicle is made by tensely adhering a transparent pellicle film made of a highly light transmitting material such as cellulose nitrate, cellulose acetate, fluorine-containing polymer and the like to one of the two annular frame faces of a pellicle frame made of aluminum, stainless steel, polyethylene or the like, using as the glue either a solvent capable of dissolving the pellicle film, which is applied to said annular frame face (hereinafter this face is called “upper frame face”) and then air-dried before receiving the film (ref. IP Publication 1), or an adhesive such as acrylic resin, epoxy resin or the like (ref. IP Publication 2). The other annular frame face (hereinafter called “lower frame face”) of the pellicle frame is paved with an agglutinant made of polybutene resin, polyvinyl acetate resin, acrylic resin, silicone resin or the like for attaching the pellicle frame to a photo mask, and over this agglutinant layer is laid the release liner (tape) to protect the agglutinant layer.
In a case wherein, after a pellicle such as the kind explained above is adhered to a face of a photo mask, a photo resist film formed on a semiconductor wafer or an original plate for making a liquid crystal panel is exposed to a light via the photomask, a foreign matter such as dust is caught on the pellicle surface and thus is prevented from reaching the surface of the photo mask so that it is possible to avoid the effect of the foreign particle such as dust if the exposure light is emitted in a manner such that the focus occurs at the pattern formed on the photo mask.
In recent years, the semiconductor devices and the liquid display board have undergone further heightening in integration and densification. Currently, a lithographic patterning on the density level of 32 nm is on the verge of realization. Such patterning can be effectively achieved by improved technologies such as immersion exposure method and double exposure method, which use a conventional argon fluoride (ArE) exmimer lasar, to which the photo resist film is exposed.
However, the next-generation semiconductor devices and the liquid display board are being demanded to have even denser patterning of a level of 10 nm or further, and the exposure technology depending on excimer laser no longer can improve itself to answer the demand of making such a dense pattern of the level of 10 nm or denser.
Now, as a most promising method for forming a pattern of a density of 10 nm or denser, an EUV exposure technology which uses an EUV light of a dominant wavelength of 13.5 mm is in the spotlight. To achieve a pattern formation on the density level of as high as 10 nm or denser on the photoresist film, it is necessary to solve the technical problems with regard to the choices of light source, photoresist, pellicle, etc., and in respect of light source and photoresist there have been considerable progresses and various proposals have been made.
With respect to a pellicle that improves yields of semiconductor device products or liquid crystal displays, IP Publication 3 discloses a silicon film of a thickness of 0.1-2.0 micrometers to act as a pellicle film for EUV lithography which is transparent and does not give rise to optical distortion; however there remain problems unsolved yet which still prevent realization of the EUV light exposure technology.